1. Field of the Invention
This invention relates to a process for the production of mono-halothiophenol and thiophenol.
Mono-halothiophenols, in particular, chlorothiophenols, are useful intermediates in the manufacture of dyes and insecticides. In particular, para-chlorothiophenol has become an important commercial chemical, its principle current use being as an intermediate in the synthesis of pesticides.
Thiophenols are useful as additives to lubricating oils, as intermediates in organic synthesis, as insecticides, fungicides and parasiticides and as ingredients of insecticidal, fungicidal and parasiticidal compositions, and are useful in the preparation of synthetic resins, rubber, vulcanization accelerators, and the like.
2. Prior Art
U.S. Pat. No. 2,490,257 to Crowley et al. describes the production of thiophenols by a vapor phase reaction of chlorobenzene and hydrogen sulfide in the presence of a catalyst, such as wood charcoal or alumina. Yields, are, however, low.
Japanese Pat. No. 1970-19046 describes the production of thiophenols by a vapor phase reaction of chloro or bromobenzene with hydrogen sulfide in the presence of a catalyst of a sulfide of Cu, Ag, Zn, Cd, Pb, Bi, Co, or Mo supported on activated carbon.
U.S. Pat. No. 3,799,989 to Sherk et al. describes the production of thiophenols at increased yields by the vapor phase reaction of chlorobenzene and hydrogen sulfide in a reactor containing a noncatalytic filler and with recycling of certain byproducts.
Japanese Pat. No. 1971-8293 describes the production of thiophenols by the vapor phase reaction of chlorobenzene and hydrogen sulfide in the presence of a catalyst, such as activated charcoal or alumina, and with recycling of certain byproducts.
The entire disclosures of all of the aforementioned references, including the Related Application, are incorporated herein by reference.
Para-chlorothiophenol is typically made from chlorobenzene by chlorosulfonation, followed by metal acid reduction. Unfortunately, such a process is too costly to yield a low priced para-chlorothiophenol.
The aforementioned Crowley et al. reference indicates that the reaction of para-dichlorobenzene with hydrogen sulfide in the presence of charcoal produces para-dithiophenol (col. 4, l. 65). The aforementioned Sherk et al. reference also implies that all the halo substituents on the aromatic ring will be replaced by --SH when a dihalobenzene is reacted with hydrogen sulfide. The reference further indicates that benzene is normally a major byproduct from the reaction of chlorobenzene with hydrogen sulfide (col. 1, l. 28-51).